With the implementation of the Stage II DPB Rule as well as the increased used of chloramination for secondary disinfection, more emphasis has been placed on maintaining water quality in distribution systems. A key component of distribution systems are the storage tanks and reservoirs, yet they often are responsible for water quality degradation due to short-circuiting, poor mixing, and increased water age. Until recently, the causes of short-circuiting, stratification and poor mixing in water storage tanks were not well understood and therefore methods to solve water quality problems were often "shots in the dark" and unsuccessful. Some state’s rules and regulations have taken a proactive step in recommending to separate the inlet and outlet pipe, but this simple recommendation is often not enough due to the complexity of mixing in different styles of storage tanks. The effect of temperature differences alone between the inlet (source) water and tank water can completely change the circulation and mixing patterns of storage tanks resulting in water quality degradation.

This technical webinar will provide the attendees a fundamental understanding of mixing processes in all styles of water storage tanks. The deficiencies of single inlet and outlet pipes, and the impact of temperature differences between inlet water and tank water, are demonstrated. The improved mixing efficiency of multi-port manifolds is presented. Other methods are also discussed (baffles,= recirculation pumps, mechanical mixers, etc.). The discussion is supported by the use of CFD and Physical Scale models so the attendees will actually see short-circuiting and mixing in storage tanks. Several "before and after" case studies are presented using field sampling data that shows the elimination of stratification, improvement in residuals, and reduction in water age.

COST:Illinois Section AWWA Members: FREE; Nonmembers: $30.00

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